Electric cable and method of manufacturing it



June 28, 1938. E. P. BARRETT ELECTRIC CABLE AND METHOD OF MANUFACTURING IT Original Filed June 23, 1932 N urs INVENTOR E. P. BARRETT ATTORNEY Patented June 28, 1938 UNITED STATES PATENT OFFICE ELECTRIC CABLE AND METHOD OF MANUFACTURING IT Application June 23, 1932, Serial No. 618,861

' Renewed November 6, 1937 12 Claims.

some instances in connection with the manufacture of cables fortransmitting intelligence electrically to form the cable by stranding pairs of paper insulated conductors together, binding the conductor pairs in a group and finally extruding a sheath of lead or lead alloy over the insulated conductors.

If in place of the lead sheath a thin metal sheath of copper, zinc, or similar metal is applied as a tape directly over a group of assembled conductors having its abutting edges secured in a manner to provide a water-proof cable joint, the

tape may have a tendency to rip and crack if the assembled cable is flexed beyond certain limits.

According to one embodiment of the invention herein illustrated and described, a flexible cable is constructed by forming pairs of paper insulated conductors, binding the pairs of conductors into a group, covering the group with a layer of paper applied helically, applying a deformed metal tape around the conductor core, the deformation preferably having the form of or including embossings or corrugations transverse to the insulated conductor portion, and the edges of the tape longitudinal to the conductor portion and soldering or otherwise joining the edges of the metal tape together to form a water-tight cable sheath and applying a suitable protecting coating over the deformed metal tape such as rubber or a wrapping of a textile material impregnated with a preserving material.

Other objects and advantages of the invention will appear from the following detailed description when considered in connection with the accompanying drawing, in which Fig. l is an elevation view of one embodiment of an apparatus, with a portion thereof cut away, for forming an electric cable such as shown in Figs. 4 and 5, and by means of which the method may be practiced;

2 is a plan view of one embodiment of the deformed tape having corrugations transverse to tape, before it is applied over the insulated conductor pairs;

Fig. 3 is an enlarged partial end view of the deforming or corrugating rollers shown in Fig. 1 for corrugating the tape;

Fig. 4 is a vertical sectional view of a cable taken along the line 4-4 of Fig. 5, and

Fig. 5 is a plan view, partially in section, of one embodiment of the cable.

Referring to the drawing (Figs. 4 and 5) a plurality of conductors I0, preferably of copper and having low resistance, insulated with paper, textile or other suitable material and preferably twisted together in pairs are stranded together loosely in layers to form a group or bundle I2. The group or bundle l2 may be formed in any suitable manner but preferably by the usual and well known form of strander, which has associ- 1 ated therewith a tape serving head by which a paper wrapping l3 may be applied spirally to retain the group comprising the conductors within a predetermined diameter.

A supply reel M (Fig. 1) containing a length of the paper covered conductor group I5 is mounted on suitable supporting members l6. Another supply reel i7 containing a length of a suitable metallic tape l8 such as brass, copper, or zinc tape is preferably mounted on supporting members IS. A pair of corrugating rollers 22 and 23 are preferably mounted on the supporting members l6, (2. portion of one of which has been shown cut away) to form a corrugated metal tape 24, the corrugations preferably extending the entire width of the tape and at right angles to the tape as shown in Fig. 2. When the edges of the tape 24 are to be lapped and soldered after the tape is formed around the conductor group I5, they are preferably coated with solder along the edges, as shown at 20 and 2| in Fig. 2. The solder coating is preferably applied to the edges before the corrugating operation.

The forming or corrugating rollers 22 and 23 (Figs. 1 and 3) are preferably constructed so that they will form corrugations by an approximately pure bending operation and without appreciably elongating the metal tape l8 and to form corrugations having approximately the shape of a sine wave. In a particular embodiment the following dimensions for the rollers were found satisfactory for producing corrugations having the above characteristics in tape approximately .005 in. thick; outside diameter 1.006 in.; 30 teeth with straight sides .030 in. wide, .05 in. deep and .015 in. radius at ends thereof, distance between centers of adjacent teeth .1 in. at a distance of .478 in. from the roller centers. Corrugating rollers having these dimensions will produce a corrugated tape having approximately .1 in. between corrugations extending in the same direction and approximately .05 in. between the upper and lower corrugations, when the teeth of one roller are kept centered in the spaces between the teeth of the other roller.

A forming roller 25 having a half-round peripheral groove therein and a forming shoe 26 are provided so that the conductor group I5 can be forced against the central portion of the corrugated tape 24 to form or curve the bottom or central portion of the tape. A forming roller 21 having a half-round peripheral groove therein and a guide roller 28 are provided to form or curve one side of the corrugated tape 24 around the insulated conductor group I5 and another similar forming roller 29 with its associated guide roller 20 are provided to form or curve the other side of the corrugated tape 24 around the insulated conductor group IS. A suitable device 3| is provided to Join the edges 0! the corrugated tape 24 in order to form a water-tight joint between the edges of the tape. Where the edges of the tape are to be lapped and have been previously coated with solder, this device may take the form of a tube 32 heated to melt the solder and secure the edges of the tape together to form a water-tight joint. Obviously, if the edges of the tape 24 are to be joined by welding or brazing the heated tube 3| may be replaced by suitable apparatus to hold the tape edges together and weld or braze them to form a water-tight joint. A take-up spool 33 is preferably provided to receive the assembled corrugated tape covered conductor group. The take-up spool 33 and the corrugating rollers 22 and 23 may be driven through suitable driving means from a suitable source of power such as a motor 34.

The operation of the device as shown in Fig. l is as follows:

As the motor 34 rotates the take-up spool 33, the paper covered conductor group I5 is drawn from the supply reel l4. The rotation of the corrugating rollers 22 and 23 causes the metal tape I! to be drawn from the supply reel il through the rollers and forms the corrugated tape 24 which passes between the forming roller 25 and the forming shoe 28. The paper insulated conductor group I5 is drawn between the forming roller 25 and forming shoe 26 above the central portion of the corrugated tape 24. As the forming roller 25 is curved the paper covered conductor group I5 is forced against the corrugated tape 24 and forms the central portion of the corrugated tape 24. As the corrugated tape 24 and the conductor group 15 pass between the forming roller 21 and its associated guide roller 28, one side of the corrugated tape 24 is formed and as the conductor group and corrugated tape pass through the forming roller 29 and its associated guide roller 30 the other side of the corrugated tape is formed. As the conductor group with the corrugated metal tape formed around it pass through the device 3| the edges of the tape are joined to form a cable which is water-tight and shielded from extraneous inductive interference. In the corrugated sheath thus made, the corrugations are complete rings around the sheath, as clearly indicated in Fig. 5, each corrugation being independent of any other. Hence of the corrugated sheath be damaged by external force or accident water or any other foreign substance so permitted to enter is dammed back at the first undamaged corrugation instead of being led along as would be the case if the corrugation were a continuous spiral. Damage by accident is thus confined to the immediate neighborhood of an injury.

In some instances it is preferable to apply a non-metallic covering over the corrugated tape. A suitable protective coating 35 (Figs. 4 and 5) such as tough rubber, gutta percha, or gutta percha substitute, may be applied by forcing the cable through an extruding machine of any suitable type well known in the art which applies a covering in one or more layers around the entire length of the cable or the protective coating may take the form of a textile material imprcg nated with a suitable preserving compound pref erably such as asphalt flooded burlap wrapped around the cable and covered with a layer of paper 35 spirally applied over the impregnazcd textile material. The textile material may be impregnated either before or after being applied to the cable and the preserving compound may be asphalt or any other similar compound capable of resisting chemical decomposition and also serving as a mechanical reenforcement for thr cable.

The above described methods of forming an electric cable provide a flexible cable which when flexed will cause the sheath 24 to crinkle uniformly and the finished cable can withstand many fiexures and may be flexed to a greater degree without the tendency of the water-tight sheath 24 to rip or crack. The fact that the corrugated sheath 24 touches the smoothly cylindrical, wrapped core l2, l3 substantially only at the bottoms of the troughs of the corrugations as clearly shown in Fig. 5) is one reason for the greater flexibility of the completed cable as compared with some cables of the prior art in which corrugations have been pressed into a completed smoothly cylindrical sheath, and in which the corrugations are pressed into and filled with the insulating material of the core.

It is to be understood that the invention is not to be limited to the particular embodiments shown, nor to the particular arrangements that have been described and shown in detail, but only by the scope of the appended claims.

What is claimed is:

1. The method of making a flexible watertight and electrically shielded electric cable which comprises forming transverse corrugations in a metal tape, forming the tape longitudinally over an insulated conductor, and joining the edges of the tape together to form a continuous transversely corrugated water-proof sheath.

2. The method of making a flexible water-tight and electrically shielded electric cable which comprises forming transverse corrugations in a metal tape by crimping without materially elongating the tape, iorming the tape longitudinally over an insulatedconductor, and joining the edges of the tape together to form a continuous transversely corrugated water-proof sheath.

3. The method of making a flexible water-tight and electrically shielded electric cable which comprises forming transverse corrugations in a metal tape, forming the tape longitudinally over an insulated conductor, joining the edges of the tape together to form a continuous transversely corrugated water-proof sheath, and applying a non-metallic covering over the corrugated sheath.

4. The method of making a flexible water-tight and electrically shielded electric cable which comprises forming transverse corrugations in a metal tape, forming the tape longitudinally over an insulated conductor, joining the edges of the tape together to form a continuous transversely corrugated water-proof sheath, and applying a wrapping of textile material impregnated with I preserving material over the corrugated sheath.

5. The method or making a flexible water-tight and electrically shielded electric cable which comprises forming transverse. corrugations in a metal tape, forming the tape longitudinally over an insulated conductor, and joining the edges of the tape together to form a continuous transversely corrugated water-proof sheath, in which each corrugation is a ring around the sheath independent of any other corrugation.

6. The method of making a flexible water-tight and electrically shielded electric cable which comprises forming transverse corrugations in a metal tape, forming the tape longitudinally over an insulated conductor, and soldering the edges of the tape together to form a continuous transversely corrugated water-proof sheath.

'7. The method of making a flexible water-tight and electrically shielded electric cable which comprises forming transverse corrugations in a metal tape, forming the tape longitudinally over an insulated conductor, and soldering the edges of the tape together to form a continuous transversely corrugated water-proof sheath, in which each corrugation is a ring around the sheath independent of any other corrugation.

8. The method oi making a flexible water-tight and electrically shielded electric cable 'which comprises forming transverse corrugations in a metal tape, forming the tape longitudinally over an insulated conductor, and joining the edges of the tape together with the ends of each corrugatlon matched together to form a continuous transversely corrugated water-proof sheath.

9. In an electric cable, a central insulated conductive core, and a flexible water-proof metallic sheath thereover consisting of a metallic tape extending longitudinally of the core and formed into a tube therearound and having its edges joined together and formed with transverse corsheath touching the insulated conductive core' substantially only at the bottoms of the troughs of the corrugations.

11. In an electric cable, a substantially nonplastic central insulated conductive core, and a flexible waterproof corrugated metallic sheath thereover consisting of a precorrugated metallic tape extending longitudinally of the core and formed into a tube therearound, the bottoms of the troughs of the corrugations tightly engaging the substantially non-plastic central insulated conductive core, the tops of the troughs of the corrugations being out of engagement with the conductive core, the corrugations extending transversely entirely around the cable, and the ends of each corrugation matched together.

v 12. In an electric cable, an inner insulated conductor portion and a flexible. metallic sheath thereover formed with circumferential corrugations, each corrugation being a complete ring around the sheath independent of any other corrugation, and the metallic sheath touching the inner insulated conductor portion substantially only at the bottoms of the troughs of the corrugations, the parts being so disposed and proportioned that seepage of accidentally introduced liquid along the insulated ed by the corrugations.

. ELLIOTT P. BARRETT.

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